Economist William Nordhaus takes a pop at the sixteen concerned scientists, in the latest skirmish kicked off by their Wall Street Journal editorial.

My response is primarily designed to correct their misleading description of my own research; but it also is directed more broadly at their attempt to discredit scientists and scientific research on climate change.1 I have identified six key issues that are raised in the article, and I provide commentary about their substance and accuracy. They are:

Is the planet in fact warming?

Are human influences an important contributor to warming?

Is carbon dioxide a pollutant?

Are we seeing a regime of fear for skeptical climate scientists?

Are the views of mainstream climate scientists driven primarily by the desire for financial gain?

Is it true that more carbon dioxide and additional warming will be beneficial?

Reader Comments (130)

CO2 is a pollutant because I say it is.Oh, really? On the basis that Nordhaus argues from every species on earth has been polluting by its very existence since it first developed lungs.And the day that the EPA actually becomes an independent objective scientific body will for sure be the day that pigs take to the skies.And I agree with mac.

Surely question 2 should be quantified - i.e. "How much of an important factor are human influences warming?" with a subsidiary question "Of the human influences, how much is due to CO2?".

Unfortunately Nordhaus quotes the IPCC as saying "“No climate model using natural forcings [i.e., natural warming factors] alone has reproduced the observed global warming trend in the second half of the twentieth century.” which says in other words human influence is >0

And he utterly fails to address point 1, that there has been little or no appreciable warming in last ten years. His rebuttal to this is to shows a chart that does indeed show no appreciable warming in the last ten years then to say it's warmer than it was 100 years ago. WTF?

The US Clean Air Act defined an air pollutant as “any air pollution agent or combination of such agents, including any physical, chemical, biological, radioactive…substance or matter which is emitted into or otherwise enters the ambient air.” In a 2007 decision on this question, the Supreme Court ruled clearly on the question: “Carbon dioxide, methane, nitrous oxide, and hydrofluorocarbons are without a doubt ‘physical [and] chemical…substance[s] which [are] emitted into…the ambient air.’

It seems that by the US Clean Air definition of a pollutant, the biggest pollutant of all is oxygen, which most certainly is "a substance which is emitted into the ambient air."

I await Nordhaus's suggestions for ridding the planet of this troublesome pollutant.

Richard Tol's greatest contribution to mankind? Concluding that CO2 is a pollutant.

Somehow I am convinced that Tol doesn't think himself as holding that hot potato.

New Zealand wants to reduce greenhouse gases because its sheep fart too much globe to take. Australia? Well, I don't know why they want their carbon tax. Britain wants to be a world leader in reducing emissions. Among all however, the United States has the stupidest reason to 'regulate CO2'. Carbon di-oxide is a pollutant

Another clown full of his own self importance, pontificates on something of which he knows not a thing. This [the Nordhaus piece] is climate advocacy for kids - doesn't he realise that Al Gore did all this stuff in his execrable [an inconvenient truth] film? An economist indeed - how does that make his views relevant? Isn't that eejit Lord Stern also an economist of some sort?

Cripes William, at least stick to something you pretend to know about.

Since William Norhaus depends for his defintion of "pollutant" on US law, does this not mean that elsewhere in the world, where there is no such definition, carbon dioxide is entirely innocent? Maybe another serious case for extradition?

Nordhaus writes, quoting the WSJ article "The first claim is that the planet is not warming. More precisely, “Perhaps the most inconvenient fact is the lack of global warming for well over 10 years now.”." He then goes on to show a graph showing the rise in temperatures over the last 130 years. While it's not evident in the WSJ article, Lindzen's recent talk makes perfectly clear that there is no disagreement on the long-term trend - he wrote the global average temperature has increased by "on the order of 0.7C over the past 150 years". Nordhaus's graph shows the recent flattening of the temperatures. Nordhaus and the WSJ16 are in violent agreement. Nordhaus may feel it's misleading because the WSJ article only alludes to the (long-term) global warming while explicitly discussing the recent slowdown, but surely he's aware that there is no real disagreement there. Nordhaus's "The last decade of temperature ... data is not representative of the longer-term trends" dismisses the recent history with an unstated (and unproven) assumption that the long-term trend can be extrapolated into the future.

Nordhaus continues with "A second argument is that warming is smaller than predicted by the models." He then answers a different question, which is whether warming is entirely attributable to natural causes. He waves away the actual objection with the casual "calculations including human sources track the actual temperature trend very closely." Perhaps it depends on what one means by "very closely" -- is a factor of two close enough?

[So far at least in his article,] Nordhaus seems to be deliberately trying to find points to dispute, rather than engaging and trying to identify points of correspondence.

I come back to my constant argument ...Why is that reasonable and intelligent human beings, faced with the possibility (I pitch it no higher) that it's not actually as bad as we thought, still insist on taking the catastrophe as highly likely? I would have thought that any slowing down of global warming that would result in less cause for alarm would have been the signal for at least a little cautious optimism.Instead they behave as if they actively want the catastrophes they predict. This is not sane behaviour.

I disagree with Nordhaus and the Supreme Court that CO2 is a pollutant. I prefer to reserve that word for something that is toxic. CO2 is not. My lungs are full of it. CO2 feeds plants.

CO2 is an externality, an unintended and uncompensated consequence of energy use. My work (and Nordhaus') shows that CO2 is a negative externality in that the expected net impacts of climate change are negative at the margin.

Our work, if correct, would justify a modest carbon tax. That carbon tax would certainly be higher than the current carbon tax in most countries (which is zero), but it would be much lower than suggested by the rhetoric of environmentalists and selected politicians.

Help me here. If no climate model has been shown to be skillful at a regional level, we cannot know the impacts at a regional level. If we cannot know the impacts at a regional level, how can we know that global warming has net negative impact?

HaroldW: Isn't the importance of the recent hiatus in warming that it has taken place against around an 8% increase of CO2 in the atmosphere. If this sort of thing happened in an engineering environment all bets would be off until it was fully understood why the temperature hadn't increased in line with CO2 increases, as predicted by the IPCC models. In climate science they'll say it's because of sulphates or some other parameter they can wiggle in their models.

"Cripes William, at least stick to something you pretend to know about."

Athelstan, keep in the front of your mind that the establishment have been persuaded that CAGW sceptics are the equivalent of flat-earthers, troofers and creationists. they start out with the view that they're of superior intelligence, and it shows. What we're seeing is the same attitude adopted by Paul Nurse, Steven Jones, John Beddington and the rest of the insulated scientific establishment. they think we're thick as two short planks and they have a right to deny our expressing our views, while they pontificate on the basis of the science which none of them fully understand. Neither do I, but I'm not standing by while the environmentalists have a go at dismantling a society that is able to feed, clothe and educate almost every citizen.

It's even worse than that. Not only is there no reliable correlation between atmospheric CO2 and temperature; there also isn't any correlation between atmospheric CO2 and human emissions of CO2. It is plausibly conjectured that there should be but it has never AFAIK been observed.

So human CO2 emissions do not demonstrably tie to net atmospheric CO2 levels which in turn do not demonstrably tie to temperature.

Let's face it, O2 is a much worse pollutant - toxic to myriads of bacteria and other primitive life forms on which the rest of the eco-system depends. It's just a matter of semantics, but anyone who argues against CO2 as a plant fertiliser is ignorant and stupid.

He argues a $10B investment yielding $50Bn is better than a $1Bn investment yielding $10Bn. But surely, given finite resources, it would be better to make ten x $1Bn bets with a 10:1 return rather than than one highly uncertain £10Bn bet with a 5:1 return? He seems to be arguing for the State to make huge monolithic bets using our money - rather than allowing millions of individuals to make their own diverse investments.

In his penultimate paragraph he appears to argue we should throw rational economic analysis out the window if there's even the tiniest chance of man-made thermogeddon. In which case we should also spend $Trillions building a giant death ray to defend the earth against invasion by little green men.

Having read 6 pages of his nonsense I'm wondering why our boys decided to quote this guy's study in their letter? He sounds like a text book alarmist and I would be highly sceptical of anything he wrote.

The man may be an economist, but somewhat like Stern, I didn't recall him predicting the fall of Lehman Brothers. I didn't recall him predicting the global economic slow down. He also knows Sweet FA about climate & computer modelling. We don't even know for sure what all the carbon sinks & sources are, they are simply estimates. We don't know about water vapour & clouds with any real certainty. I could go on. The computer models are full to the brim with assumptions about feedbacks, both positive & negative, & largely rely on positive feedbacks to produce the warming observed. As to the solar effects, if you simply devalue the effect it might or might not have, it will no doubt show that natural factors cannot have produced the observed warming, models are also infinitely tunable, & just because they give the answer you were looking for or even desired doesn't make them right! His logic is deeply flawed, rather like his scientists' computer models.

You do not need a precise forecast for the regional impacts of climate change in order to assess the impacts. You only need a probabilistic forecast. If 60% of the models say it will get wetter in a particular place, and 40% that it will get drier, then you estimate the impacts of a wetting and a drying, and you take the average of those as your expected impact.

In fact, uncertainty drives up the impact of climate change. A substantial share of the economic impact of climate change is made up of adaptation costs. It is rather more costly to prepare for the possibility of drying and wetting than to prepare for either drying or wetting.

Following on from Harold's comment, Nordhaus' statement that the 16 claimed "that the planet is not warming" is not just lacking precision. It was clearly not what the 16 stated at all. They clearly acknowledged that the planet is warming in their next paragraph when referring to

"the smaller-than-predicted warming over the 22 years since the U.N.'s Intergovernmental Panel on Climate Change (IPCC) began issuing projections"

This is the issue that Nordhaus would rather not face. As Gerald North said in 2001,

“There are so many adjustables in the models and there is a limited amount of observational data, so we can always bring the models into agreement with the data.”

Hindcasting with dubious assumptions is not convincing, particularly when different models assume different quantities for the same thing. The only test of models with any value is forecasting. In this the models fail by consistently exaggerating climate sensitivity. The more reliable estimate derived from 150 years of observations is insufficient to justify alarm.

As for drawing parallels with tobacco, Nordhaus is casting the wrong group as the villains. It's the "hockey team" that hid the decline - even from their fellow lead authors in 1999/2000. They also prevented proper examination of their paleo data and methodology for as long as they could. And then we have Gleik and the obscenely funded NGOs.

It is Jones and Stocker that cooked up the new IPCC confidentiality rules that deny not just the sceptics, the public and IPCC Expert Reviewers access the review comments and Lead Authors responses on the AR5 dafts.

The changes in the Appendix A Procedures, which they sneaked through under the guise of InterAcdemy Council recommendations, mean that not even the government members of the IPCC will be able to check if review comments from each draft are properly addressed before the governments have to accept the AR5 Report.

The HUBRIS is so thick it seems to have stopped all the bloodflow to his brain.

Wouldn't it be fun to get him on the stand in a courtroom as an expert witness and cross-examine him in front of a jury? There is so much material here with which to slice him and dice him that I suspect he would check himself into a hospital rather than show up for a 2d day of fun.

You are so deep in the forest that you've missed the Bishop's point. The particular manner with which the witches approach the examination of the entrails is of no interest to those of us who aren't witches until someone demonstrates that the entrails have predictive ability. We really don't care if they are supposed to be stirred clockwise or counterclockwise or for how long or with what type of stick.

I guess in an old-style financial setting we would be talking of opportunity gains but for some reason impacts are only negative when climate change is involved. No wonder costs rise with uncertainties.

You do not need a precise forecast for the regional impacts of climate change in order to assess the impacts. You only need a probabilistic forecast. If 60% of the models say it will get wetter in a particular place, and 40% that it will get drier, then you estimate the impacts of a wetting and a drying, and you take the average of those as your expected impact.

I suggest William Briggs would go to town on this. It is absolutely barking mad.

Consider:

My tarot card reader foretells that I will win $1 million next year.My Clarevoyant foretells that I will win $5 million next year.

I averaged the predictions and estimated my exped increase in total wealth next year as $3 million. So I went and bought a big yacht today.

Our work, if correct, would justify a modest carbon tax. That carbon tax would certainly be higher than the current carbon tax in most countries (which is zero), but it would be much lower than suggested by the rhetoric of environmentalists and selected politicians.

I have far less problem with that than any other proposed policy measure.

In fact, uncertainty drives up the impact of climate change. A substantial share of the economic impact of climate change is made up of adaptation costs. It is rather more costly to prepare for the possibility of drying and wetting than to prepare for either drying or wetting.

But is anyone really using regional climate models in this way? And do you really think they should be?

Some stations are warming all of the time (very rare)Some warmed for some of the timeSome didn't warm.Some are definitely cooler than they were in the 30s/40s.Some that did warm aren't warming anymore.Some are cooling a lot recently.Some months for some station are warming while some are cooling.

I assume Gekko was making the same point I was. Tol makes the same questionable assumption that Nordhaus makes -- that other supposed experts have produced reliable work upon which they can do their magic. Of course, they have to make this assumption or there is nothing for them to do. We don't have to make this assumption, especially given all the evidence that the work of these other 'experts' is NOT reliable.